The present invention pertains to hard disk drives, and, more importantly, to an electronic device for driving an actuator device for a hard disk and for driving a motor that turns the hard disk.
As is known, rather complex electronic devices are used for driving hard disks, commonly referred to as xe2x80x9cCOMBOsxe2x80x9d, which comprise circuits dedicated to driving the motor that turns the hard disk and to driving the actuator device of the hard disk itself, A/D and D/A converters, digital circuits, power blocks, and so on.
In greater detail, FIG. 1 shows a hard disk 1, which is positioned inside a container 2 and is provided with a plurality of tracks for data storage. The hard disk 1 is connected by means of a hub 4 to a shaft 5, which is in turn connected to an electric motor 6 (xe2x80x9cspindlexe2x80x9d), which causes rotation of the hard disk 1 about the shaft 5 at a constant rate. The electric motor 6 is driven by an electronic device 7, connected to the motor itself by means of a first flexible cable 8.
In addition, the electronic device 7 drives, via a second flexible cable 9 and a third flexible cable 10, respectively a first actuation stage 11 and a second actuation stage 12 of an actuator device 13.
In detail, the first actuation stage 11 consists of an induction motor (also referred to as xe2x80x9cvoice coil motorxe2x80x9d) to which a suspension 15 formed by a lamina is fixed in cantilever fashion. The suspension 15 ends with a flexible portion 16 which carries, at its free end, a read/write transducer 17 (xe2x80x9csliderxe2x80x9d) and a pair of actuators 18a and 18b made of piezoelectric material, one set on one side, and the other set on the other side, of the floating end of the flexible portion 16. The flexible portion 16 and the piezoelectric actuators 18a, 18b constitute the second actuation stage 12 of the actuator device 13. In particular, each piezoelectric actuator 18a, 18b consists of a chip of piezoelectric material set between two metal plates that form the two electrodes of the actuator; one electrode is connected to the flexible portion 16 (ground), whilst the other is floating.
Advantageously, the read/write transducer 17 is fixed to the flexible portion 16 by means of a gimbal 19. In addition, the read/write transducer 17 supports a read/write head 20 which constitutes the reading and writing device proper of the hard disk 1.
The first actuation stage 11 displaces the ensemble made up of the suspension 15 and of the read/write transducer 17 through the hard disk 1 during track search (rough displacement), whilst the second actuation stage 12 carries out fine control of the position of the read/write transducer 17, following the track (finer regulation).
In particular, the flexible portion 16 converts the mechanical deformation undergone by the piezoelectric actuators 18a, 18b as a result of a potential applied to their floating electrodes into a linear displacement of the read/write transducer 17. To a first approximation, apart from hysteresis phenomena due to a non-unique relation between the potential applied to the floating electrodes of the piezoelectric actuators 18a, 18b and the mechanical deformation undergone by the piezoelectric actuators themselves, we will find that for positive potentials applied to the floating electrodes there is obtained a displacement of the read/write transducer 17 in a first direction, whilst for negative potentials applied to the floating electrodes, the read/write transducer 17 is displaced in a second direction opposite to the first.
For this purpose, each piezoelectric actuator 18a, 18b is driven by means of an amplifier circuit which is included in the electronic device 7 and has both positive and negative output dynamics with respect to the ground of the actuator. Typically, amplifier circuits are used with output dynamics of dozens of volts (e.g., from xc2x112 V up to xc2x140 V).
In general, these amplifier circuits are integrated using junction-isolation techniques, exploiting reverse-biased junctions to obtain isolation of the various components making up the amplifier circuit itself. In order to prevent forward biasing of these junctions, the substrate of semiconductor material, in which the amplifier circuit is integrated, must necessarily be connected to the largest negative potential among those applied to the amplifier circuit itself (a potential which, as has been said previously, may even reach xc2x140 V).
At present, this requirement prevents these amplifier circuits from being integrated in one and the same chip of semiconductor material in which the other circuits making up the electronic device 7 are made. In fact, this chip, on account of the presence of power blocks, requires a substrate electrically connected to ground. Given that the two requirements mentioned above (substrate connected to the largest negative potential and substrate connected to ground) are mutually incompatible, it is not feasible to have an electronic device 7 that works properly and is integrated in one and the same chip of semiconductor material together with the amplifier circuits.
The technical problem that lies at the root of the present invention is to provide an electronic device that will overcome the limitations specified above with reference to the known art.
The disclosed embodiment of the invention is directed to an electronic device for driving an actuator device for a hard disk and a motor for turning the hard disk that includes a first driving circuit connected to the rotation motor and integrated in a chip of semiconductor material that has a substrate defining a reference-potential region; a second driving circuit integrated in the chip and connected to the first actuation stage; and a third driving circuit integrated in the chip and connected to the second actuation stage of the actuator device. Ideally, the third driving circuit has two amplifier circuits integrated in the chip, each connected to a respective piezoelectric actuator, each of the amplifier circuits driving a respective piezoelectric actuator to control displacements of a read/write transducer.
In accordance with another embodiment of the invention, a hard disk system is provided that includes an actuator device for a hard disk and a motor for turning the hard disk, the actuator device supporting a read/write transducer and including a first actuation stage and a second actuation stage that respectively control a first displacement and a second displacement of the read/write transducer, and the electronic device including a first driving circuit connected to the motor and integrated in a chip of semiconductor material that has a substrate defining a reference-potential region; a second driving circuit integrated in the chip and connected to the first actuation stage; and a third driving circuit integrated in the chip and connected to the second actuation stage of the actuator device.